i can only suggest that this stuff is immensely confusing to many of us. we all seek a way to clarify and simplify it. this "buddies/enemies" analogy is probably the way your instructor remembers it for herself. she probably sincerely believes she is helping you by passing this analogy on to you. i wouldn't fault her on it. but, if you can think of a different way that works for you, go with it.
fluid and electrolytes was a huge portion of my national certification exam in iv therapy. i failed the exam the first time i took it and it was by two questions. the biggest portion of questions i missed was in the fluid and electrolyte section. believed me, i studied up on this subject when i took the test the next year and passed it. part of my life journey of learning to study effectively.
in doing these charts that i'm working on, i've got 8 books that i'm using as references. for me, i have to read the information about 10 times before it sinks in. i try to find an analogy sometimes, but there are times when nothing comes to me. have you read my post on the inflammation response? when i originally was reviewing the material the one thing that came to mind was war and comparing the mast cells to hand grenades and so that is how i described it. water balloons could have also worked. others might not agree with it.